When you guys talk about 22-30% hills... what tools are you using to determine the grade? Because I have tried about half a dozen online tools and gotten half a dozen different answers.

For instance, regarding the maximum grade of one particular hill I ride routinely near my workplace:
Veloroutes : 16%
RidewithGPS : 4.8%
Mapmyride : 20%+

Now I'm comfortable saying it's more than 4.8%, but is it 16%? Is it 20%?